The present invention relates to surgical angioplasty balloon instruments and procedures. More particularly, the present invention relates to an instrument, mechanism and procedure for retracting or withdrawing a protective sheath surrounding a balloon catheter having an angioplasty stent applied thereto, prior to implanting of the stent, following retraction of the protective sheath.
In order to improve the effectiveness of vascular angioplasty in relieving blockage or repairing cardiovascular damage, stainless steel mesh stents of tubular configuration have been developed for implantation into the vascular wall of a patient. The stent is introduced by a balloon catheter, the stent being carried by the expandable balloon portion of the catheter, which is expanded to attain expansion and implantation of the stent. The catheter and stent are protected by a surrounding sheath which is maintained in place over the stent during introduction to the implantation site, and which is then retracted to expose the stent prior to the expansive implantation procedure. The protective sheath prevents any potential slippage of the stent relative to the deflated balloon before and during the introduction and location of the stent at the implantation site. In addition, the sheath will cover the stent as it passes through the patient's vascular system, such that mesh material or edges of the stent are covered during introduction, which edges or portions could lead to abrasion or damage of the vascular tissue during introduction. Once the precise implantation site has been reached, the protective sheath must be carefully retracted to expose the stent for expansion and implantation. Unintended re-advancement of the sheath can cause its forward end to catch on the stent and produce slippage on a deflated balloon, resulting in displacement of the stent from the correct vascular implantation site. These and other disadvantages are eliminated by the mechanism, instruments and method in accordance with the present invention.